Parallel analysis of multiple genes on the DNA or RNA level is becoming more and more important, because cancer is identified as a disease that involves multiple genes. To study this cascade of genetic alterations, analysis on a single-gene level cannot be the final answer. Microarray analysis is state-of-the-art technology for fulfilling these scientific needs. The OSUCCC Microarray Shared Resource (MASR) was established as a "developing" Shared Resource in 1998 initially serving investigators in the Molecular Biology and Cancer Genetics Program with genome wide expression analysis, and subsequently becoming one of the Shared Resources for the entire OSUCCC offering genome wide expression analysis using Affymetrix GeneChips. In September 2002, quantification of RNA integrity by capillary electrophoresis became available, and since September 2003, the MASR has offered validation of microarray results, via an array-based design of primers for real-time PCR. For projects utilizing any of these technologies, the MASR offers multiple services, including experimental design consultation, sample processing, hybridization, scanning, full statistical analysis and consultation, and validation of results. Newer services, such as custom arrays and SNPs are soon to be available. The MASR trains investigators to upload their results to Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/) since this becomes mandatory for publication in many journals. The MASR website (www.dnaarrays.org) contains information about services, publications and downloadable protocols and order forms. The MASR offers timely, technical and professional expertise that promotes high quality science at a competitive price. To support OSUCCC researchers, several hundred RNA samples are processed each year for genome wide expression analysis. In addition, several hundred RNA samples are processed for integrity quantification. During 2003, the MASR worked with 30 investigators, 95% of who are CCC members affiliated with four CCC programs, and the amount of MASR service to these members increased 72% over the previous year. There are 42 current or pending grants from OSUCCC members that include utilization of the MASR. The OSUCCC has provided $2.1 M in Institutional support to establish and run the MASR as a "developing" Shared Resource. We now request CCSG funding that will provide `30% of the total support for this important full Shared Resource over the next five years.